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USP 51 – Antimicrobial Effectiveness Test
USP Chapter 51, the Antimicrobial Effectiveness Test (AET) is crucial to determine the antimicrobial effectiveness of preservatives in different products including pharmaceutical and cosmetics & personal care products. It outlines a procedure for checking the efficacy of antimicrobial preservatives used to prevent microbial growth that may manifest during production or later during use.
Test Requirement
Challenge Organisms
Microorganisms such as Candida Albicans (ATCC 10231), Aspergillus niger (ATCC 16404), Escherichia coli (ATCC 4352), Pseudomonas aeruginosa (ATCC 9027), Staphylococcus aureus (ATCC 6538) are specified by this standard to challenge the preservatives.
Each organism is tested separately to determine the preservative’s effectiveness against both fungi and bacteria.
Media and preparation of inoculum
Specific media are used to grow the challenge organisms and there is a standardized procedure for the preparation of inoculum. Such a standardization aids in the generalization of the test across various laboratories and makes the test more valid.
USP <51> Testing procedure
- Test microorganisms from stock culture are taken into a sterile vessel and harvested either by centrifugation (for broth medium) or washing (for solid medium).
- These test microorganisms are resuspended in sterile saline and maintained at a microbial count of ~1 X 10^8 CFU/ml.
- The test sample is taken and initial microbial concentration in it is determined using plate count methods.
- The test sample is then placed in a sterile container and is exposed to a specific amount of test organisms.
- Inoculated test samples are incubated at 22.5 ± 2.5°C and viable count of microorganisms is determined at 7, 14, and 28 days respectively.
- The preservative effectiveness in the test product is determined by comparing microbial count at specific time intervals to the initial concentration of test microorganisms.
Industry Applications of USP 51 Test Method
This antimicrobial effectiveness test as a baseline determinant plays a significant role in most industries to check on microbial contamination in several products. This test is crucial in ensuring product quality and safety for the consumers and also for compliance in many industries.
Pharmaceutical industry
Multi-dose sterile products
This test is important for products like eye drops, nasal sprays and all injectables which are used several times once the sealed container is opened. It validates that the preservative system is capable of protecting the product from any microbial growth that could be incurred during repeated usage.
Personal care and cosmetics
Skincare and beauty products
Water and nutrient solutions present in cosmetics such as lotions, creams, and even makeup products aid microbial growth. Testing carried out by USP <51> ensures that preservatives in these products are effective in containing microbial intrusion which is important for the health of users as well as the quality of products.
Baby products
Products like baby wipes and diaper rash creams must be free from harmful microbes to prevent irritation or infection. USP Chapter 51 helps ensure these products remain safe for sensitive users.
Importance of Rigorous USP Chapter 51 Testing
USP 51 is crucial for preventing potential risks and maintaining the health of consumers. By testing the antimicrobial efficacy of preservative systems, the industry can effectively control product degradation and minimize the adverse effects on consumer health due to microbial stubbornness.
If you are in the pharmaceutical or personal care product industry and need to ensure your products meet the highest safety standards, consider partnering with Microbe Investigation Switzerland (MIS). At MIS, we provide comprehensive testing and validation services to help you comply with USP <51> and other critical safety standards.
Let MIS be your trusted partner in safeguarding your products and securing consumer confidence. Contact us today to learn more about how we can assist you in ensuring your products are safe and effective.
FAQs
This antimicrobial effectiveness testing describes the methods and criteria for testing the effectiveness of antimicrobial preservatives included in pharmaceuticals, personal care products, and other potential consumer goods. The standard ensures that the antimicrobial preservatives used are adequate to protect products from microbial contamination.
Testing is required for any aqueous-based product that includes antimicrobial preservatives, such as pharmaceuticals, cosmetics, and personal care products.
The turnaround time for USP 51 test is 4 to 5 weeks.
At Microbe Investigations, we test for the USP 51 using the following strains : Pseudomonas aeruginosa (ATCC 15442), Escherichia coli (ATCC 8739), Staphylococcus aureus (ATCC 6538P), Enterococcus hirae (ATCC 10541), Klebsiella pneumoniae (ATCC 4352), MRSA (ATCC 33591), Salmonella enterica (ATCC 10708), Candida Albicans (MTCC 3017) and Aspergillus niger (ATCC-16888).
This testing is typically conducted during product development and as part of the stability testing regimen to ensure the preservative’s effectiveness throughout the product’s shelf life.
If a product fails testing, it indicates that the preservative system is not adequate to protect the product against microbial contamination. The product formulation may need to be adjusted, or an alternative preservative system may need to be considered.
Yes, while USP 51 provides a general framework, the testing can be tailored to the specific characteristics of the product, considering factors like pH, viscosity, and the presence of non-aqueous components.
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